The present disclosure is directed to isolated peptides useful in the testing of and diagnosis of infection by the human parasite of the genus Schistosoma and to methods of testing employing such peptides.
The world distribution of schistosomiasis is typically endemic in tropical zones wherein the schistosome's life cycle is dependent on known, regionally specific intermediate snail hosts. See, Hunter's Tropical Medicine, Sixth Edition, W.D. Saunders Company, pages 713 et seq. The epidemiology of schistosomiasis typically involves geographic regions between 36.degree. north and 34.degree. south latitude and further characterized by having fresh water temperatures in the range of about 25.degree.-30.degree. C. The endemic populations include people of all ages, but the disease particularly seems to attack young boys, ages 5 to 10. The infection mechanism involves mere contact with the water of the region assuming the appropriate snail population. Other details regarding the pathology of the disease are set forth in representative sources such as the text mentioned above. Suffice it to say, it is a debilitating parasitic disease.
Present day techniques of detection of the disease in the human host primarily involve identification of the schistosome egg. There are multiple techniques available, but they primarily involve microscopic examination of human feces, and such tests are set forth in the referenced text. Prior art serologic tests have tended to be somewhat insensitive and somewhat lacking in specificity. Most serologic tests that have been developed can provide positive indication of the disease only exceedingly late after the onset of infection. By contrast, the test of the present disclosure will detect the antibody before or prior to egg production by the parasite worm in the human host.
As can be understood, the chronic symptoms of schistosome infestation are more severe than the subtle symptoms occurring prior to egg production. Thus, prior art test responses (sensitivity and specificity) are variable because impure schistosomal antigens are used. Contrary to this problem, the peptides of the present disclosure can be synthesized in substantial purity and consistency and, in that sense, represent the ultimate in available test reagents. Testing can now be carried out with a minimum of specialized laboratory equipment, even in ill-equipped field conditions in an endemic population. Thus, the peptides can be employed in testing large population groups or a single individual, and these tests can be carried out, even in the most adverse of circumstances.